1. Field of the Invention
The invention pertains to a composition useful in and a process for practicing high performance ion exchange chromatography. Materials for performing high speed liquid chromatographic analyses are known where only the thin outer surface of the chromatographic support materials is available for actively exchanging ions with liquid media.
2. Prior Art:
Parrish, in Nature 207:402 (1965), describes "superficial ion exchange chromatography" using beads of cross-linked polystyrene which bear a "shallow surface laye" of ion exchange groups. Horvath et al. describe ion exchange chromatography with glass beads having a styrenedivinylbenzene resin skin, appropriately sulfonated or aminated to produce cation and anion exchange materials which they call "pellicular resins" in reference to the skin-like layer of active sites on these beads. Analytical Chemistry 39:1422 (1967).
Iler, in U.S. Pat. No. 3,485,658 (1969), describes the preparation of chromatic materials where alternating layers of colloidal solid particles are laid down on a substrate by treating the substrate, in alternating fashion with dispersions of oppositely charged colloidal particles. These colloidal particles as described are, among others, alumina, silica and ionic synthetic polymers.
Kirkland, in U.S. Pat. No. 3,488,922 (1970), describes a method of "chromatographic separation which uses superficially porous glass beads having sorptively active crusts. " These chromatographic materials consist of a plurality of impervious glass beads which have been alternately coated with monolayers of microparticular ion exchange resins, alumina, silica and the like, using the method described by Iler.
Levendusky, in U.S. Pat. No. 3,250,702 (1966), describes the production of an ion exchange bed where particles of about equal size of both anionic and cationic resins are allowed to agglomerate or clump together to form the bed. The particles described therein are larger than about 400 mesh (about 35 microns).
Grubhofer, in German Auslegeschrift 1,045,978 (1958), describes the preparation of nonagglomerated mixed resin beds where a suspension of anion or cation exchange particles, of about 0.2 millimicrons patticle size, is contacted with one of the components of the mixed resin bed which has a charge opposite to that of the suspension particles, thereby laying down a thin layer of these suspension particles on the particles (500-1000 microns) of that component.
In U.S. Pat. No. 2,961,417 (1960), Small describes a method for avoiding agglomeration of a mixed resin bed by treatment of either the cationic or anionic resin particles with resinous polyelectrolyte solutions. Iler likewise mentions that strong electrolytes redisperse the colloidal particles from his substrate surfaces.